Maximum animal mass over 3.5 billion years of evolution – at the metabolic limit

A bound on mass specific metabolism explains a maximum animal mass with log-linear evolution for 3.5 billion years

In a classical figure, Bonner (1965) showed a continued increase in the maximum length of animals over 3.5 billion years of evolution. I recalculated length to mass (Witting, 2008, 2016) and estimated the rate of change as a function of mass, and found an almost log-linear trajectory with a dw/dt-exponent of 1.07 (left figure). While the increase wasn’t uniform (Payne et al., 2009), it illustrates a macro evolution that is bound by an upper limit on metabolism. This is confirmed also by a mass specific metabolism that is invariant of mass across taxonomic groups from bacteria to mammals (Makarieva et al., 2008; Kiørboe and Hirst, 2014).